This invention relates to the production of powder filled electric cables.
To protect multi-stranded, sheathed electric cables against the entry and migration of water it has normally been the practice to fill the voids within the sheath by coating the conductors with petroleum jelly. Because this method is slow and expensive and the product is greasy, it has recently been the practice to use powder for filling the interstices between the conductors, as described in copend-ing United States Patent Application Serial No. 556,294 filed March 7, 1975 in the name of L. V. Woytiuk entitled Water Blocked Electric Cables and assigned to Northern Electric Company Limited. One method of applying the powder to the cable core is to pass the wire conductors through an electrostatic powder coating bed before stranding but that method is slow and cannot meet the normal stranding speed of the cable.
It is an object of the present invention to pro-vide a method and apparatus for powder filling the core of a sheathed electric cable, operable at increased speeds of travel of the cable.
It is another object of the invention to provide a method and apparatus, for powder filling the core of a sheathed electric cable, which is relatively simple and inexpensive to operate.
In its broadest aspect the invention consists of a method of continuously producing an electric cable having a plurality of conductors forming a stranded core enclosed in a sheath or jacket, the voids within the sheath or jacket being at least partially filled with powder, the steps of:

1036t~2 passing the conductors in spaced lateral relationship through a closed chamber and thereafter bringing the conductors - la -together to form said core; introducing powder into the chamber continuously in the path of the conductors; collec-ting that portion of the powder settling in the chamber and recirculating the settling powder continuously into the chamber; and charging additional powder into the chamber corresponding to the decrease in the quantity of the sett-ling powder. Preferably the strands are oil coated prior to their entry into the chamber and the powder is blown into the chamber to impinge directly on the strands. The method includes powder filling the space between the inner and outer sheaths of a multi-sheathed cable.
In another aspect the invention consists of an apparatus for at least partially filling a sheathed, multi-stranded electrical cable with powder, comprising: a hous-ing having a closed chamber; means to pass a plurality of conductors in spaced lateral relationship through the cham-ber; means to introduce powder into the chamber in the path of the conductors; means to recirculate that portion of the powder settling in the chamber; and means to charge addi-tional powder into the chamber corresponding to the decrease in the quantity of the settling powder. The apparatus may also be used to provide a powder filling between the inner and outer sheaths of an electric cable.
An example embodiment of the invention is shown an the accompanying drawings in which:
Figure 1 is a plan view in cross-section showing an apparatus for powder filling a multi-stranded, sheathed electric cable.
Figure 2 is a sectional view in elevation taken along line 2-2 of Figure 1.

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The example apparatus illustrated in the drawings consists of a housing 10 providing a closed rectangular chamber 12 and having a top 14, opposed s~de walls 16, oppos-ed end walls 18, and a bottom trough 20 of semi-cylindrical shape. ~ first screw conveyor 22 is located coaxially in trough 20 and is journally mounted in end walls 18 of hous-ing 10. A layplate 24 is located in one end wall 18a of housing 10 adjacent top 14 and a closing die 26 is located in the opposite end wall 18b in axial alignment with lay-plate 24. Below layplate 24 the outlet 27 of an upstanding blower chute 28 projects through end wall 18a into chamber 12.
The central shaft 29 of first conveyor 22 carries at its ends a pair of pulleys 30 which are connected by belts 32 to a common shaft 34 journalled in mounts 36 outside hou-sing 10. One pulley 30a is coupled with a drive motor 38 axially aligned with shaft 29 of first conveyor 22. Shaft 29 of first conveyor 22 also carries an impeller 40 located in main chamber 41 of blower chute 28 outside housing 10.
Trough 20 is connected to chamber 41 of chute 28 through an opening 42 in end wall 18 of housing 10.
A hopper 43 abuts one side wall 16a of housing 10 with a semi-cylindrical bottom trough 44 in which a second journally mounted screw conveyor 46 is coaxially located.
One end of second conveyor 46 terminates at an opening 48 in side wall 16 of housing 10 and the other end of the second conveyor is axially coupled with a drive motor 50.
In the operation of the example embodiment con-ductors 60 pass through layplate 24 into chamber 12 of hous-ing 10 in spaced lateral relationship, horizontally travers-~ _ 3 _ ing upper zone 62 of the chamber and at the same time con-verging to pass through closing die 26, whence they emerge from chamber 12 as a cable core 64 in known manner.
Hopper 43 is charged with powder which is moved by second conveyor 46 through opening 48 to drop into trough 20 at the bottom of chamber 12. First conveyor 22 then moves the powder through opening 41 in end wall 18 of housing 10 into chamber 42 of chute 28 where it is forced upwardly by impeller 40 and through outlet 27 into zone 62 of chamber 12.
The outlet opening of chute 28 is designed and oriented to direct the powder into the upper portion of chamber 12 at a velocity sufficient to produce a cloud of the material in zone 62 of the chamber in the path of strands 60. Preferably the powder is directed by chute 28 to im-pinge directly onto conductors 60. To improve the adhesion of the powder to conductors 60, the conductors are usually lightly coated with oil by suitable means not shown. An-other method of causing the powder to adhere to conductors 60 is to locate a high voltage electrode at the exit to chute 28 which imparts an electrical charge to the powder as in electrostatic powder coating.
Excess powder drops back into trough 20 of cham-ber 12 where it is recirculated by conveyor 22 through chute 28 into upper zone 62 of the chamber. As the powder recirculating through chamber 12 is depleted the chamber is recharged from hopper 42 by further conveyor 46. Any suit-able means can be employed to recharge chamber 12 automati-cally. For example by governing the speed of motor 50 in-versely proportional to the torque on motor 38 a decrease in torque on conveyor 22 caused by depletion of powder in trough 20 will cause further conveyor 46 to speed up which ~ _ 4 _ 103680~
will discharge powder more rapidl~ into chamber 12. The electrical connections for establishing such a relationship - 4a -between motors 38 and 50 are well known. Hopper 42 can be charged periodically by any suitable means either manual or automatic. Other devices such as probe sensors could also be used to measure powder flow rate through the system to govern the speed of motor 50. Of course other suitable means could be employed to feed additional powder to trough 20 in chamber 12. For example first conveyor 22 could be extended from chamber 12 outwardly through end wall 18b into a bin similar to hopper 43.
It will be appreciated that the electric cable may be only partially filled with powder for effective wat-er blockage, as described in above-mentioned copending United States Application No. 556,294, and the present in-vention may be employed for that purpose. Also, the inven-tion may be used to interpose powder between the inner and outer sheaths of a cable as described in Application No.
556,294. The method and apparatus of the present invention may also be employed to fill a cable with other particulate matter such as mineral powder to provide insulation or flame retardant powder.